package utils;

import sun.misc.BASE64Decoder;
import sun.misc.BASE64Encoder;

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
import java.io.IOException;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;

/**
 * 对称加密算法AES
 */
public class AESUtils {

    private static final String KEY_ALGORITHM = "AES";

    /**
     * 默认的加密算法
     */
    private static final String DEFAULT_CIPHER_ALGORITHM = "AES/ECB/PKCS5Padding";


    /**
     * AES 加密操作
     */
    public static String encrypt(String content, String key) throws Exception {
        // 创建密码器
        Cipher cipher = Cipher.getInstance(DEFAULT_CIPHER_ALGORITHM);
        byte[] byteContent = content.getBytes("utf-8");
        // 初始化为加密模式的密码器
        cipher.init(Cipher.ENCRYPT_MODE, getSecretKey(key));
        // 加密
        byte[] result = cipher.doFinal(byteContent);
        //通过Base64转码返回
        return byte2Base64(result);
    }

    /**
     * AES 解密操作
     */
    public static String decrypt(String content, String key) throws Exception {
        //实例化
        Cipher cipher = Cipher.getInstance(DEFAULT_CIPHER_ALGORITHM);
        //使用密钥初始化，设置为解密模式
        cipher.init(Cipher.DECRYPT_MODE, getSecretKey(key));
        //执行操作
        byte[] result = cipher.doFinal(base642Byte(content));
        return new String(result, "utf-8");
    }

    /**
     * 生成加密秘钥
     */
    private static SecretKeySpec getSecretKey(final String key) {
        //返回生成指定算法密钥生成器的 KeyGenerator 对象
        try {
            KeyGenerator kg = KeyGenerator.getInstance(KEY_ALGORITHM);
            //指定算法名称
            SecureRandom random = SecureRandom.getInstance("SHA1PRNG");
            random.setSeed(key.getBytes());
            //AES 要求密钥长度为 128
            kg.init(128, random);
            //生成一个密钥
            SecretKey secretKey = kg.generateKey();
            // 转换为AES专用密钥
            return new SecretKeySpec(secretKey.getEncoded(), KEY_ALGORITHM);
        } catch (NoSuchAlgorithmException ex) {
            ex.printStackTrace();
        }
        return null;
    }

    /**
     * 字节数组转Base64编码
     */
    public static String byte2Base64(byte[] bytes) {
        BASE64Encoder encoder = new BASE64Encoder();
        return encoder.encode(bytes);
    }

    /**
     * Base64编码转字节数组
     */
    public static byte[] base642Byte(String base64Key) throws IOException {
        BASE64Decoder decoder = new BASE64Decoder();
        return decoder.decodeBuffer(base64Key);
    }

}